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<FONT color="green">001</FONT>    /*<a name="line.1"></a>
<FONT color="green">002</FONT>     * Licensed to the Apache Software Foundation (ASF) under one or more<a name="line.2"></a>
<FONT color="green">003</FONT>     * contributor license agreements.  See the NOTICE file distributed with<a name="line.3"></a>
<FONT color="green">004</FONT>     * this work for additional information regarding copyright ownership.<a name="line.4"></a>
<FONT color="green">005</FONT>     * The ASF licenses this file to You under the Apache License, Version 2.0<a name="line.5"></a>
<FONT color="green">006</FONT>     * (the "License"); you may not use this file except in compliance with<a name="line.6"></a>
<FONT color="green">007</FONT>     * the License.  You may obtain a copy of the License at<a name="line.7"></a>
<FONT color="green">008</FONT>     *<a name="line.8"></a>
<FONT color="green">009</FONT>     *      http://www.apache.org/licenses/LICENSE-2.0<a name="line.9"></a>
<FONT color="green">010</FONT>     *<a name="line.10"></a>
<FONT color="green">011</FONT>     * Unless required by applicable law or agreed to in writing, software<a name="line.11"></a>
<FONT color="green">012</FONT>     * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.12"></a>
<FONT color="green">013</FONT>     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.13"></a>
<FONT color="green">014</FONT>     * See the License for the specific language governing permissions and<a name="line.14"></a>
<FONT color="green">015</FONT>     * limitations under the License.<a name="line.15"></a>
<FONT color="green">016</FONT>     */<a name="line.16"></a>
<FONT color="green">017</FONT>     <a name="line.17"></a>
<FONT color="green">018</FONT>    package org.apache.commons.beanutils;<a name="line.18"></a>
<FONT color="green">019</FONT>    <a name="line.19"></a>
<FONT color="green">020</FONT>    import java.util.Map;<a name="line.20"></a>
<FONT color="green">021</FONT>    import java.util.WeakHashMap;<a name="line.21"></a>
<FONT color="green">022</FONT>    <a name="line.22"></a>
<FONT color="green">023</FONT>    /**<a name="line.23"></a>
<FONT color="green">024</FONT>     * An instance of this class represents a value that is provided per (thread)<a name="line.24"></a>
<FONT color="green">025</FONT>     * context classloader.<a name="line.25"></a>
<FONT color="green">026</FONT>     * <a name="line.26"></a>
<FONT color="green">027</FONT>     * &lt;p&gt;Occasionally it is necessary to store data in "global" variables<a name="line.27"></a>
<FONT color="green">028</FONT>     * (including uses of the Singleton pattern). In applications which have only<a name="line.28"></a>
<FONT color="green">029</FONT>     * a single classloader such data can simply be stored as "static" members on<a name="line.29"></a>
<FONT color="green">030</FONT>     * some class. When multiple classloaders are involved, however, this approach<a name="line.30"></a>
<FONT color="green">031</FONT>     * can fail; in particular, this doesn't work when the code may be run within a<a name="line.31"></a>
<FONT color="green">032</FONT>     * servlet container or a j2ee container, and the class on which the static<a name="line.32"></a>
<FONT color="green">033</FONT>     * member is defined is loaded via a "shared" classloader that is visible to all<a name="line.33"></a>
<FONT color="green">034</FONT>     * components running within the container. This class provides a mechanism for<a name="line.34"></a>
<FONT color="green">035</FONT>     * associating data with a ClassLoader instance, which ensures that when the<a name="line.35"></a>
<FONT color="green">036</FONT>     * code runs in such a container each component gets its own copy of the<a name="line.36"></a>
<FONT color="green">037</FONT>     * "global" variable rather than unexpectedly sharing a single copy of the<a name="line.37"></a>
<FONT color="green">038</FONT>     * variable with other components that happen to be running in the same<a name="line.38"></a>
<FONT color="green">039</FONT>     * container at the same time (eg servlets or EJBs.)&lt;/p&gt;<a name="line.39"></a>
<FONT color="green">040</FONT>     *<a name="line.40"></a>
<FONT color="green">041</FONT>     * &lt;p&gt;This class is strongly patterned after the java.lang.ThreadLocal<a name="line.41"></a>
<FONT color="green">042</FONT>     * class, which performs a similar task in allowing data to be associated<a name="line.42"></a>
<FONT color="green">043</FONT>     * with a particular thread.&lt;/p&gt;<a name="line.43"></a>
<FONT color="green">044</FONT>     *<a name="line.44"></a>
<FONT color="green">045</FONT>     * &lt;p&gt;When code that uses this class is run as a "normal" application, ie<a name="line.45"></a>
<FONT color="green">046</FONT>     * not within a container, the effect is identical to just using a static <a name="line.46"></a>
<FONT color="green">047</FONT>     * member variable to store the data, because Thread.getContextClassLoader<a name="line.47"></a>
<FONT color="green">048</FONT>     * always returns the same classloader (the system classloader).&lt;/p&gt;<a name="line.48"></a>
<FONT color="green">049</FONT>     *<a name="line.49"></a>
<FONT color="green">050</FONT>     * &lt;p&gt;Expected usage is as follows:&lt;br&gt;<a name="line.50"></a>
<FONT color="green">051</FONT>     * &lt;pre&gt;<a name="line.51"></a>
<FONT color="green">052</FONT>     *  public class SomeClass {<a name="line.52"></a>
<FONT color="green">053</FONT>     *    private static final ContextClassLoaderLocal global <a name="line.53"></a>
<FONT color="green">054</FONT>     *      = new ContextClassLoaderLocal() {<a name="line.54"></a>
<FONT color="green">055</FONT>     *          protected Object initialValue() {<a name="line.55"></a>
<FONT color="green">056</FONT>     *              return new String("Initial value");<a name="line.56"></a>
<FONT color="green">057</FONT>     *          };<a name="line.57"></a>
<FONT color="green">058</FONT>     *<a name="line.58"></a>
<FONT color="green">059</FONT>     *    public void testGlobal() {<a name="line.59"></a>
<FONT color="green">060</FONT>     *      String s = (String) global.get();<a name="line.60"></a>
<FONT color="green">061</FONT>     *      System.out.println("global value:" + s);<a name="line.61"></a>
<FONT color="green">062</FONT>     *      buf.set("New Value");<a name="line.62"></a>
<FONT color="green">063</FONT>     *    }<a name="line.63"></a>
<FONT color="green">064</FONT>     * &lt;/pre&gt;<a name="line.64"></a>
<FONT color="green">065</FONT>     * &lt;/p&gt;<a name="line.65"></a>
<FONT color="green">066</FONT>     *<a name="line.66"></a>
<FONT color="green">067</FONT>     * &lt;p&gt;&lt;strong&gt;Note:&lt;/strong&gt; This class takes some care to ensure that when<a name="line.67"></a>
<FONT color="green">068</FONT>     * a component which uses this class is "undeployed" by a container the<a name="line.68"></a>
<FONT color="green">069</FONT>     * component-specific classloader and all its associated classes (and their<a name="line.69"></a>
<FONT color="green">070</FONT>     * static variables) are garbage-collected. Unfortunately there is one<a name="line.70"></a>
<FONT color="green">071</FONT>     * scenario in which this does &lt;i&gt;not&lt;/i&gt; work correctly and there<a name="line.71"></a>
<FONT color="green">072</FONT>     * is unfortunately no known workaround other than ensuring that the<a name="line.72"></a>
<FONT color="green">073</FONT>     * component (or its container) calls the "unset" method on this class for<a name="line.73"></a>
<FONT color="green">074</FONT>     * each instance of this class when the component is undeployed. The problem<a name="line.74"></a>
<FONT color="green">075</FONT>     * occurs if:<a name="line.75"></a>
<FONT color="green">076</FONT>     * &lt;ul&gt;<a name="line.76"></a>
<FONT color="green">077</FONT>     * &lt;li&gt;the class containing a static instance of this class was loaded via<a name="line.77"></a>
<FONT color="green">078</FONT>     * a shared classloader, and&lt;/li&gt;<a name="line.78"></a>
<FONT color="green">079</FONT>     * &lt;li&gt;the value stored in the instance is an object whose class was loaded<a name="line.79"></a>
<FONT color="green">080</FONT>     * via the component-specific classloader (or any of the objects it refers<a name="line.80"></a>
<FONT color="green">081</FONT>     * to were loaded via that classloader).&lt;/li&gt;<a name="line.81"></a>
<FONT color="green">082</FONT>     * &lt;/ul&gt;<a name="line.82"></a>
<FONT color="green">083</FONT>     * The result is that the map managed by this object still contains a strong<a name="line.83"></a>
<FONT color="green">084</FONT>     * reference to the stored object, which contains a strong reference to the<a name="line.84"></a>
<FONT color="green">085</FONT>     * classloader that loaded it, meaning that although the container has<a name="line.85"></a>
<FONT color="green">086</FONT>     * "undeployed" the component the component-specific classloader and all the<a name="line.86"></a>
<FONT color="green">087</FONT>     * related classes and static variables cannot be garbage-collected. This is<a name="line.87"></a>
<FONT color="green">088</FONT>     * not expected to be an issue with the commons-beanutils library as the only<a name="line.88"></a>
<FONT color="green">089</FONT>     * classes which use this class are BeanUtilsBean and ConvertUtilsBean and<a name="line.89"></a>
<FONT color="green">090</FONT>     * there is no obvious reason for a user of the beanutils library to subclass<a name="line.90"></a>
<FONT color="green">091</FONT>     * either of those classes.&lt;/p&gt;<a name="line.91"></a>
<FONT color="green">092</FONT>     *<a name="line.92"></a>
<FONT color="green">093</FONT>     * &lt;p&gt;&lt;strong&gt;Note:&lt;/strong&gt; A WeakHashMap bug in several 1.3 JVMs results in <a name="line.93"></a>
<FONT color="green">094</FONT>     * a memory leak for those JVMs.&lt;/p&gt;<a name="line.94"></a>
<FONT color="green">095</FONT>     *<a name="line.95"></a>
<FONT color="green">096</FONT>     * &lt;p&gt;&lt;strong&gt;Note:&lt;/strong&gt; Of course all of this would be unnecessary if<a name="line.96"></a>
<FONT color="green">097</FONT>     * containers required each component to load the full set of classes it<a name="line.97"></a>
<FONT color="green">098</FONT>     * needs, ie avoided providing classes loaded via a "shared" classloader.&lt;/p&gt;<a name="line.98"></a>
<FONT color="green">099</FONT>     * <a name="line.99"></a>
<FONT color="green">100</FONT>     * @see java.lang.Thread#getContextClassLoader  <a name="line.100"></a>
<FONT color="green">101</FONT>     * @author Eric Pabst<a name="line.101"></a>
<FONT color="green">102</FONT>     */<a name="line.102"></a>
<FONT color="green">103</FONT>    public class ContextClassLoaderLocal {<a name="line.103"></a>
<FONT color="green">104</FONT>        private Map valueByClassLoader = new WeakHashMap();<a name="line.104"></a>
<FONT color="green">105</FONT>        private boolean globalValueInitialized = false;<a name="line.105"></a>
<FONT color="green">106</FONT>        private Object globalValue;<a name="line.106"></a>
<FONT color="green">107</FONT>    <a name="line.107"></a>
<FONT color="green">108</FONT>        /**<a name="line.108"></a>
<FONT color="green">109</FONT>         * Construct a context classloader instance<a name="line.109"></a>
<FONT color="green">110</FONT>         */<a name="line.110"></a>
<FONT color="green">111</FONT>        public ContextClassLoaderLocal() {<a name="line.111"></a>
<FONT color="green">112</FONT>            super();<a name="line.112"></a>
<FONT color="green">113</FONT>        }<a name="line.113"></a>
<FONT color="green">114</FONT>    <a name="line.114"></a>
<FONT color="green">115</FONT>        /**<a name="line.115"></a>
<FONT color="green">116</FONT>         * Returns the initial value for this ContextClassLoaderLocal<a name="line.116"></a>
<FONT color="green">117</FONT>         * variable. This method will be called once per Context ClassLoader for<a name="line.117"></a>
<FONT color="green">118</FONT>         * each ContextClassLoaderLocal, the first time it is accessed <a name="line.118"></a>
<FONT color="green">119</FONT>         * with get or set.  If the programmer desires ContextClassLoaderLocal variables<a name="line.119"></a>
<FONT color="green">120</FONT>         * to be initialized to some value other than null, ContextClassLoaderLocal must<a name="line.120"></a>
<FONT color="green">121</FONT>         * be subclassed, and this method overridden.  Typically, an anonymous<a name="line.121"></a>
<FONT color="green">122</FONT>         * inner class will be used.  Typical implementations of initialValue<a name="line.122"></a>
<FONT color="green">123</FONT>         * will call an appropriate constructor and return the newly constructed<a name="line.123"></a>
<FONT color="green">124</FONT>         * object.<a name="line.124"></a>
<FONT color="green">125</FONT>         *<a name="line.125"></a>
<FONT color="green">126</FONT>         * @return a new Object to be used as an initial value for this ContextClassLoaderLocal<a name="line.126"></a>
<FONT color="green">127</FONT>         */<a name="line.127"></a>
<FONT color="green">128</FONT>        protected Object initialValue() {<a name="line.128"></a>
<FONT color="green">129</FONT>            return null;<a name="line.129"></a>
<FONT color="green">130</FONT>        }<a name="line.130"></a>
<FONT color="green">131</FONT>    <a name="line.131"></a>
<FONT color="green">132</FONT>        /** <a name="line.132"></a>
<FONT color="green">133</FONT>         * Gets the instance which provides the functionality for {@link BeanUtils}.<a name="line.133"></a>
<FONT color="green">134</FONT>         * This is a pseudo-singleton - an single instance is provided per (thread) context classloader.<a name="line.134"></a>
<FONT color="green">135</FONT>         * This mechanism provides isolation for web apps deployed in the same container. <a name="line.135"></a>
<FONT color="green">136</FONT>         * @return the object currently associated with the context-classloader of the current thread. <a name="line.136"></a>
<FONT color="green">137</FONT>         */<a name="line.137"></a>
<FONT color="green">138</FONT>        public synchronized Object get() {<a name="line.138"></a>
<FONT color="green">139</FONT>            // synchronizing the whole method is a bit slower <a name="line.139"></a>
<FONT color="green">140</FONT>            // but guarantees no subtle threading problems, and there's no <a name="line.140"></a>
<FONT color="green">141</FONT>            // need to synchronize valueByClassLoader<a name="line.141"></a>
<FONT color="green">142</FONT>            <a name="line.142"></a>
<FONT color="green">143</FONT>            // make sure that the map is given a change to purge itself<a name="line.143"></a>
<FONT color="green">144</FONT>            valueByClassLoader.isEmpty();<a name="line.144"></a>
<FONT color="green">145</FONT>            try {<a name="line.145"></a>
<FONT color="green">146</FONT>                <a name="line.146"></a>
<FONT color="green">147</FONT>                ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();<a name="line.147"></a>
<FONT color="green">148</FONT>                if (contextClassLoader != null) {<a name="line.148"></a>
<FONT color="green">149</FONT>                    <a name="line.149"></a>
<FONT color="green">150</FONT>                    Object value = valueByClassLoader.get(contextClassLoader);<a name="line.150"></a>
<FONT color="green">151</FONT>                    if ((value == null) <a name="line.151"></a>
<FONT color="green">152</FONT>                    &amp;&amp; !valueByClassLoader.containsKey(contextClassLoader)) {<a name="line.152"></a>
<FONT color="green">153</FONT>                        value = initialValue();<a name="line.153"></a>
<FONT color="green">154</FONT>                        valueByClassLoader.put(contextClassLoader, value);<a name="line.154"></a>
<FONT color="green">155</FONT>                    }<a name="line.155"></a>
<FONT color="green">156</FONT>                    return value;<a name="line.156"></a>
<FONT color="green">157</FONT>                    <a name="line.157"></a>
<FONT color="green">158</FONT>                }<a name="line.158"></a>
<FONT color="green">159</FONT>                <a name="line.159"></a>
<FONT color="green">160</FONT>            } catch (SecurityException e) { /* SWALLOW - should we log this? */ }<a name="line.160"></a>
<FONT color="green">161</FONT>            <a name="line.161"></a>
<FONT color="green">162</FONT>            // if none or exception, return the globalValue <a name="line.162"></a>
<FONT color="green">163</FONT>            if (!globalValueInitialized) {<a name="line.163"></a>
<FONT color="green">164</FONT>                globalValue = initialValue();<a name="line.164"></a>
<FONT color="green">165</FONT>                globalValueInitialized = true;<a name="line.165"></a>
<FONT color="green">166</FONT>            }//else already set<a name="line.166"></a>
<FONT color="green">167</FONT>            return globalValue;<a name="line.167"></a>
<FONT color="green">168</FONT>        }<a name="line.168"></a>
<FONT color="green">169</FONT>    <a name="line.169"></a>
<FONT color="green">170</FONT>        /** <a name="line.170"></a>
<FONT color="green">171</FONT>         * Sets the value - a value is provided per (thread) context classloader.<a name="line.171"></a>
<FONT color="green">172</FONT>         * This mechanism provides isolation for web apps deployed in the same container. <a name="line.172"></a>
<FONT color="green">173</FONT>         * <a name="line.173"></a>
<FONT color="green">174</FONT>         * @param value the object to be associated with the entrant thread's context classloader<a name="line.174"></a>
<FONT color="green">175</FONT>         */<a name="line.175"></a>
<FONT color="green">176</FONT>        public synchronized void set(Object value) {<a name="line.176"></a>
<FONT color="green">177</FONT>            // synchronizing the whole method is a bit slower <a name="line.177"></a>
<FONT color="green">178</FONT>            // but guarentees no subtle threading problems<a name="line.178"></a>
<FONT color="green">179</FONT>            <a name="line.179"></a>
<FONT color="green">180</FONT>            // make sure that the map is given a change to purge itself<a name="line.180"></a>
<FONT color="green">181</FONT>            valueByClassLoader.isEmpty();<a name="line.181"></a>
<FONT color="green">182</FONT>            try {<a name="line.182"></a>
<FONT color="green">183</FONT>                <a name="line.183"></a>
<FONT color="green">184</FONT>                ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();<a name="line.184"></a>
<FONT color="green">185</FONT>                if (contextClassLoader != null) {<a name="line.185"></a>
<FONT color="green">186</FONT>                    valueByClassLoader.put(contextClassLoader, value);<a name="line.186"></a>
<FONT color="green">187</FONT>                    return;<a name="line.187"></a>
<FONT color="green">188</FONT>                }<a name="line.188"></a>
<FONT color="green">189</FONT>                <a name="line.189"></a>
<FONT color="green">190</FONT>            } catch (SecurityException e) { /* SWALLOW - should we log this? */ }<a name="line.190"></a>
<FONT color="green">191</FONT>            <a name="line.191"></a>
<FONT color="green">192</FONT>            // if in doubt, set the global value<a name="line.192"></a>
<FONT color="green">193</FONT>            globalValue = value;<a name="line.193"></a>
<FONT color="green">194</FONT>            globalValueInitialized = true;<a name="line.194"></a>
<FONT color="green">195</FONT>        }<a name="line.195"></a>
<FONT color="green">196</FONT>        <a name="line.196"></a>
<FONT color="green">197</FONT>        /** <a name="line.197"></a>
<FONT color="green">198</FONT>         * Unsets the value associated with the current thread's context classloader<a name="line.198"></a>
<FONT color="green">199</FONT>         */<a name="line.199"></a>
<FONT color="green">200</FONT>        public synchronized void unset() {    <a name="line.200"></a>
<FONT color="green">201</FONT>            try {<a name="line.201"></a>
<FONT color="green">202</FONT>            <a name="line.202"></a>
<FONT color="green">203</FONT>                ClassLoader contextClassLoader = Thread.currentThread().getContextClassLoader();<a name="line.203"></a>
<FONT color="green">204</FONT>                unset(contextClassLoader);<a name="line.204"></a>
<FONT color="green">205</FONT>                <a name="line.205"></a>
<FONT color="green">206</FONT>            } catch (SecurityException e) { /* SWALLOW - should we log this? */ }<a name="line.206"></a>
<FONT color="green">207</FONT>        }<a name="line.207"></a>
<FONT color="green">208</FONT>        <a name="line.208"></a>
<FONT color="green">209</FONT>        /** <a name="line.209"></a>
<FONT color="green">210</FONT>         * Unsets the value associated with the given classloader<a name="line.210"></a>
<FONT color="green">211</FONT>         * @param classLoader The classloader to &lt;i&gt;unset&lt;/i&gt; for<a name="line.211"></a>
<FONT color="green">212</FONT>         */<a name="line.212"></a>
<FONT color="green">213</FONT>        public synchronized void unset(ClassLoader classLoader) {    <a name="line.213"></a>
<FONT color="green">214</FONT>            valueByClassLoader.remove(classLoader);<a name="line.214"></a>
<FONT color="green">215</FONT>        }    <a name="line.215"></a>
<FONT color="green">216</FONT>    }<a name="line.216"></a>




























































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